Lithium sulfur battery cathode material and preparation method thereof

Abstract

The invention relates to a lithium sulfur battery cathode material and a preparation method thereof and belongs to the technical field of lithium sulfur batteries. The lithium sulfur battery cathode material comprises a sulfur-containing active cathode material, a conductive additive, a binding agent and a sulfur carrier, wherein the sulfur carrier is porous basic manganese oxide, a graphene-basicmanganese oxide composite or a graphene-basic manganese oxide-cobalt sulfide composite. The sulfur carrier is good in conductivity and dispersibility, capable of favorably bonding with an intermediate product of sulfur and a lithium-sulfur battery, good in processability and easy to coat to form a lithium ion battery electrode. The synthesis method is simple in process operation, environment-friendly, free of calcination and low in energy consumption and has an industrialized prospect.

Description

technical field [0001] The invention belongs to the technical field of lithium-sulfur batteries, and in particular relates to a lithium-sulfur battery cathode material and a preparation method thereof. Background technique [0002] Lithium-sulfur batteries have a theoretical discharge specific capacity (1675mAh / g) and high energy density (2600Wh / kg), and are considered to be one of the most promising new batteries. The theoretical specific capacity of elemental sulfur to lithium is 1675mAh / g, the average discharge voltage of the battery is 2.2V, and the theoretical energy density of lithium-sulfur batteries reaches 2600Wh / kg, which is much higher than the theory of lithium-ion batteries such as lithium iron phosphate and ternary materials. Energy Density. In addition, sulfur is abundant in nature, and it is also an industrial by-product with low price. Sulfur is environmentally friendly and has obvious advantages. [0003] However, there are still many challenges and defec...

AI Technical Summary

Problems solved by technology

[0003] However, there are still many challenges and defects to be solved in lithium-sulfur batteries: 1. The lithium polysulfide generated during the discharge process will break away from the current collector and enter the electrolyte, causing the active material to peel off from the conductive carrier, resulting in an increase in the internal resistance of the battery. During the process, some lithium polysulfides will be redoxed and deposited on the surface of the electrode, resulting in the loss of active materials; in addition, during charging, the long-chain lithium polysulfides will migrate to the negative electrode and react with lithium ions to form short-chain lithium polysulfides. A part will generate insulating Li 2 S 2 and lithium sulfide precipitation, the above process is repeated during the charging and discharging process, forming a shuttle effect and eventually causing the loss of active materials, reducing Coulombic efficiency and battery life

2. The conductivity of the active material is poor, and the sulfur and discharge product Li 2 S 2 It has poor conductivity with lithium sulfide, so it is necessary to add a conductive agent to increase the conductivity of the active material, thus reducing the mass specific capacity of the battery

On the other hand, the generated lithium sulfide will be deposited on the surface of the electrode, further preventing the battery reaction, making the reaction incomplete, and reducing the utilization rate of the active material.

3. Volume effect, the density of sulfur is 2.07g / cm 3 , while the density of lithium sulfide is 1.66g / cm 3 , so after the complete reaction, the volume expansion rate reaches 80%, which will lead to the collapse of the material structure during repeated charging and discharging, resulting in a rapid decay of capacity and thus affecting the cycle life of the battery.

[0004] Combining graphene with sulfur can improve the conductivity of the active material and help reduce the Coulomb effect and volume effect. In the Chinese patent CN105609707A, a method for preparing a manganese dioxide hollow sphere lithium-sulfur battery cathode material is disclosed. Manganese dioxide, sulfur element, and graphene are combined to make lithium-sulfur battery cathode materials. The specific capacitance of the prepared lithium-sulfur battery after 100 cycles is reduced to about 75% of the initial specific capacitance, and the number of battery cycles is not limited. battery life

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